2000 Elantra wont shift into 4th!!
 

Okay, so im really considering trading my truck for this Elantra and only have tonight to decide. The guy im trading let me take the car home for a night to make sure it feels correct and in doing so i have found out that there is no 3rd to 4th shift.. 1st 2nd and 3rd shift like an absolute dream but i just get absolutly nothing from 4th! Ran a code reader and got back codes P0734 Which was "4th gear incorrect ratio", and P0713 which was "temp sensor high." Can someone please tell me if the transmission is shot in this thing or if its just a matter of playing with some wires and sensors???!! I only have until 10 AM to decide!

I dont know if it helps or not, but i also got code P1624 as well...
Everything says possible open or short circuit.. could that be it???

Well, heck.. I'll take a stab at it. Don't know about the second code you posted, but the first deals with high temp in the trans fluid, so I assume this is an automatic (information you left out). Could be that bands for 4th gear got cooked. Automatics don't like it when the fluid gets too hot, nor do they like it when the fluid runs low. Check the level of the fluid, but you might call a trans shop for an opinion. Will it still be a good deal if you need to replace the transmission? Only you know the answer to that.